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Thanks to Dr. Tim Bracey, MBCHB, PhD, Derriford Hospital (England), for contributing this case. To contribute a Case of the Week, follow the guidelines on our Case of the Week page.

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Case of the Week #288

Clinical History:
A 65 year old man presented with a large mass in the floor of the mouth (levels Ia to VI), but mostly suprahyoid. Ultrasound showed a vascular appearance and a normal appearing thyroid gland.

Micro images:

MRI

Core biopsy

What is your diagnosis?

Diagnosis:
Metastatic hepatocellular carcinoma to floor of mouth

Discussion:
In this case, the pathologists knew of the patient's prior history of hepatocellular carcinoma, treated with TACE, with a rising serum alpha-fetoprotein.

The core biopsy shows a trabecular pattern of tumor cells separated by tortuous "sinusoid-like" vascular channels. At high power, the pleomorphic tumor cells have well defined cytoplasmic boundaries, a "hepatoid appearance" with abundant pink cytoplasm and prominent nucleoli. Bile plugs are easily seen (arrows).

The tumor cells are immunoreactive for HepPar1 and hyaline globules are positive for DPAS:

Left: HepPar1, right: DPAS

Other immunostains (not shown) were pCEA with a canalicular staining pattern and CD34+ sinusoid-like channels.

Worldwide, hepatocellular carcinoma (HCC) is the most common solid tumor and the #3 leading cause of cancer-related deaths (US National Cancer Institute).
It is relatively uncommon in the US with 21,670 estimated deaths in 2013, although its incidence is rising due to hepatitis C virus infection. Metastases are initially within the liver, with late distant metastases to the adrenal gland, bone, lung and porta hepatis lymph nodes (PathologyOutlines.com). The floor of mouth is an unusual site of metastatic spread, and HepPar1 and AFP are recommended as markers of extrahepatic metastases (Int J Clin Exp Pathol 2013;6:816). Multiple simultaneous carcinomas of the floor of mouth, although rare, should be excluded by careful histologic examination (Jpn J Clin Oncol 1994;24:166).